(a) Field of the Invention
The present invention relates to a modified Gauss type photographic lens system and, more particularly, to a standard photographic lens system which is compact and light in weight.
(b) Description of the Prior Art
For standard photographic lens systems to be used for single-lens reflex cameras, a large aperture ratio and long back focal length are generally required and, therefore, modified Gauss type lens systems are widely used. Known modified Gauss type lens systems, however, have the following disadvantages. That is, when this type of lens system is made small in size, it is unavoidable that flare due to coma, curvature of field, spherical aberration, etc. become unfavourable. When glass materials of high refractive indices are used in order to make aberrations favourable, weight of the lens system increases and, moreover, the cost of materials becomes high.